This invention relates to a retractable leash for animals, having a housing containing a spring-biased reel in which the remaining length of leash can be taken up and which is stoppable by means of an actuating mechanism.
Compared to conventional leashes, retractable leashes have the advantage that they automatically wind up excess leash on a spring-biased reel. If desired, the length to which the leash can extend can be set temporarily by actuating a key. By actuating another push-to-lock key, the length to which the leash extends can be set permanently. The advantage of setting a permanent leash length is that the leash will be halted at the set length without a key having to be actuated. The disadvantage, however, is that the leash no longer winds up automatically. If the length to which the leash is extended falls short of the length set, the leash will drag on the ground and may get dirty. Moreover, the animal or the person in charge of it can get their legs caught up in the leash, or, since a leash dragging on the ground may be difficult to detect, passers-by may trip over it.
The DE 85 09 585 U1 describes a device which seeks to overcome the disadvantages described above. In this publication, the basic problem was recognized and an initial approach to solving it is described. With this device, the extension length of the leash can be additionally limited to one particular length predetermined by the design. For example, as is described in this publication, the extension can be limited to about half the leash length. This limitation, however, is dependent on the wind-up diameter of the spring-biased winding reel, which means that the accuracy of the limitation is determined by the number of layers of leash on the reel. Depending on the kind of leash cord, one layer corresponds to about one meter of unrolled leash. If the leash does not roll up on the reel in strictly parallel windings, but in superposed windings, the length of leash that can be extended can vary by one to two meters. The device is designed in such manner that the pawl described in the publication engages when the given length of leash has been released, thus halting any further release. However, on account of the hysteresis (difference between engaging and disengaging) inherent in the design, the leash must roll up by at least two layers, i.e. it must retract by about two meters, before the pawl disengages again and falls back into its initial position.
All in all, the described device has three major disadvantages. Firstly, only one intermediate leash length can be activated, which makes handling very inconvenient; after all, it's a serious disadvantage if a leash measuring, say, 7 m in length, can only be set to a single intermediate length. Secondly, even this set length is subject to unpredictable and strong variation depending on the way the leash winds up on the reel. This is something the person in charge cannot influence. Accordingly, he or she cannot rely on the leash's always blocking after the same length of leash has been released. Particularly in town, this can lead to an incalculable risk. The third disadvantage is that the leash must retract (roll up) by a considerable amount in order for the locking mechanism to disengage and allow the leash to be released anew and stopped again when necessary. In practice, this is contrary to the intended purpose of a retractable leash, which is to allow the animal as much freedom of movement as possible, and not to have to train it to behave in a certain way before it can be taken for a walk on this kind of leash.
Sometimes an animal will bite through its leash close to its point of attachment. The leash will then retract at very high speed, with a danger of its loosely-jerking free end injuring anyone nearby. At any rate, the leash will wind completely onto the spring-biased reel and will no longer be accessible from outside the housing.
To restore the leash to working order, the entire housing has to be opened up. The reel's spring has to be tensioned again, and the housing then reassembled part by part.
If the leash is not preset with a key, animals will often bound away too quickly for the person in charge to stop them. They may cover several meters—for example to chase after another animal—before they are stopped. This can lead to unpredictable, dangerous situations. The abruptness with which an animal is stopped in such a situation, moreover, poses the risk of neck injuries to the animal, with potentially serious consequences.
The object of this invention is thus to create a retractable leash that does not have these disadvantages.